108 research outputs found
Cosmological Hydrodynamics with Multi-Species Chemistry and Nonequilibrium Ionization and Cooling
We have developed a method of solving for multi-species chemical reaction
flows in non--equilibrium and self--consistently with the hydrodynamic
equations in an expanding FLRW universe. The method is based on a backward
differencing scheme for the required stability when solving stiff sets of
equations and is designed to be efficient for three-dimensional calculations
without sacrificing accuracy. In all, 28 kinetic reactions are solved including
both collisional and radiative processes for the following nine separate
species: H, H+, He, He+, He++, H-, H2+, H2, and e-. The method identifies those
reactions (involving H- and H2+) ocurring on the shortest time scales,
decoupling them from the rest of the network and imposing equilibrium
concentrations to good accuracy over typical cosmological dynamical times.
Several tests of our code are presented, including radiative shock waves,
cosmological sheets, conservation constraints, and fully three-dimensional
simulations of CDM cosmological evolutions in which we compare our method to
results obtained when the packaged routine LSODAR is substituted for our
algorithms.Comment: Latex and postscript, 24 pages, with 6 figures. The paper is also
available at http://zeus.ncsa.uiuc.edu:8080/~abel/PGas/bib.html Submitted to
New Astronom
Design and Flight Performance of NOAA-K Spacecraft Batteries
The US National Oceanic and Atmospheric Administration (NOAA) operates the Polar Operational Environmental Satellite (POES) spacecraft (among others) to support weather forecasting, severe storm tracking, and meteorological research by the National Weather Service (NWS). The latest in the POES series of spacecraft, named as NOAA-KLMNN', one is in orbit and four more are in various phases of development. The NOAA-K spacecraft was launched on May 13, 1998. Each of these spacecraft carry three Nickel-Cadmium batteries designed and manufactured by Lockheed Martin. The battery, which consists of seventeen 40 Ah cells manufactured by SAFT, provides the spacecraft power during the ascent phase, orbital eclipse and when the power demand is in excess of the solar array capability. The NOAA-K satellite is in a 98 degree inclination, 7:30AM ascending node orbit. In this orbit the satellite experiences earth occultation only 25% of the year. This paper provides a brief overview of the power subsystem, followed by the battery design and qualification, the cell life cycle test data, and the performance during launch and in orbit
Transport of interface states in the Heisenberg chain
We demonstrate the transport of interface states in the one-dimensional
ferromagnetic Heisenberg model by a time dependent magnetic field. Our analysis
is based on the standard Adiabatic Theorem. This is supplemented by a numerical
analysis via the recently developed time dependent DMRG method, where we
calculate the adiabatic constant as a function of the strength of the magnetic
field and the anisotropy of the interaction.Comment: minor revision, final version; 13 pages, 4 figure
Performance of Nickel-Cadmium Batteries on the POES Series of Weather Satellites
The advanced Television Infrared Observation satellite program is a cooperative effort between the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), the United Kingdom, Canada and France, for providing day and night global environmental and associated data. NASA is responsible for procurement launch, and checkout of these spacecraft before transferring them over to NOAA, who operates the spacecraft to support weather forecasting, severe storm tracking, and 'meteorological research by the National Weather Service. These spacecraft with all weather monitoring instruments imposed challenging requirements for the onboard electrical power subsystem (EPS). This paper provides first a brief overview of the overall power subsystem, followed by a description of batteries. A unique power subsystem design which provides 'tender-loving-care' to these batteries is highlighted. This is followed by the on-orbit maintenance and performance data of the batteries since launch
On the Ortho:Para Ratio of H3+ in Diffuse Molecular Clouds
The excitation temperature T_01 derived from the relative intensities of the
J = 0 (para) and J = 1 (ortho) rotational levels of H2 has been assumed to be
an accurate measure of the kinetic temperature in interstellar environments. In
diffuse molecular clouds, the average value of T_01 is ~70 K. However, the
excitation temperature T(H3+) derived from the (J,K) = (1,1) (para) and (1,0)
(ortho) rotational levels of H3+ has been observed to be ~30 K in the same
types of environments. In this work, we present observations of H3+ in three
additional diffuse cloud sight lines for which H2 measurements are available,
showing that in 4 of 5 cases T_01 and T(H3+) are discrepant. We then examine
the thermalization mechanisms for the ortho:para ratios of H3+ and H2,
concluding that indeed T_01 is an accurate measure of the cloud kinetic
temperature, while the ortho:para ratio of H3+ need not be thermal. By
constructing a steady-state chemical model taking into account the
nuclear-spindependence of reactions involving H3+, we show that the ortho:para
ratio of H3+ in diffuse molecular clouds is likely governed by a competition
between dissociative recombination with electrons and thermalization via
reactive collisions with H2.Comment: 13 pages, 8 figures, 5 tables, accepted for publication in Ap
Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data
The magnitude of marine plankton net community production (NCP) is indicative of both the biologically driven exchange of carbon dioxide between the atmosphere and the surface ocean and the export of organic carbon from the surface ocean to the ocean interior. In this study the seasonal variability in the NCP of five biogeochemical regions in the North Atlantic was determined from measurements of surface water dissolved oxygen and dissolved inorganic carbon (DIC) sampled from a Volunteer Observing Ship (VOS). The magnitude of NCP derived from dissolved oxygen measurements (NCPinline image) was consistent with previous geochemical estimates of NCP in the North Atlantic, with an average annual NCPinline image of 9.5 ± 6.5 mmol O2 m−2 d−1. Annual NCPinline image did not vary significantly over 35° of latitude and was not significantly different from NCP derived from DIC measurements (NCPDIC). The relatively simple method described here is applicable to any VOS route on which surface water dissolved oxygen concentrations can be accurately measured, thus providing estimates of NCP at higher spatial and temporal resolution than currently achieved
ART^2 : Coupling Lyman-alpha Line and Multi-wavelength Continuum Radiative Transfer
Narrow-band Lya line and broad-band continuum have played important roles in
the discovery of high-redshift galaxies in recent years. Hence, it is crucial
to study the radiative transfer of both Lya and continuum photons in the
context of galaxy formation and evolution in order to understand the nature of
distant galaxies. Here, we present a three-dimensional Monte Carlo radiative
transfer code, All-wavelength Radiative Transfer with Adaptive Refinement Tree
(ART^2), which couples Lya line and multi-wavelength continuum, for the study
of panchromatic properties of galaxies and interstellar medium. This code is
based on the original version of Li et al., and features three essential
modules: continuum emission from X-ray to radio, Lya emission from both
recombination and collisional excitation, and ionization of neutral hydrogen.
The coupling of these three modules, together with an adaptive refinement grid,
enables a self-consistent and accurate calculation of the Lya properties. As an
example, we apply ART^2 to a cosmological simulation that includes both star
formation and black hole growth, and study in detail a sample of massive
galaxies at redshifts z=3.1 - 10.2. We find that these galaxies are Lya
emitters (LAEs), whose Lya emission traces the dense gas region, and that their
Lya lines show a shape characteristic of gas inflow. Furthermore, the Lya
properties, including photon escape fraction, emergent luminosity, and
equivalent width, change with time and environment. Our results suggest that
LAEs evolve with redshift, and that early LAEs such as the most distant one
detected at z ~ 8.6 may be dwarf galaxies with a high star formation rate
fueled by infall of cold gas, and a low Lya escape fraction.Comment: 20 pages, 16 figures, accepted for publication in MNRA
Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set
The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets
The Galactic Distribution of Asymptotic Giant Branch Stars
We study the Galactic distribution of ~10,000 Asymptotic Giant Branch (AGB)
stars selected by IRAS colors and variability index. The distance to each star
is estimated by assuming a narrow luminosity function and a model-derived
bolometric correction. The characteristic AGB star luminosity, L_AGB, is
determined from the condition that the highest number density must coincide
with the Galactic bulge. Assuming a bulge distance of 8 kpc, we determine L_AGB
\~ 3,500 Lo, in close agreement with values obtained for nearby AGB stars using
the HIPPARCOS data. We find that there are no statistically significant
differences in the Galactic distribution of AGB stars with different IRAS
colors, implying a universal density distribution. The direct determination of
this distribution shows that it is separable in the radial, R, and vertical, z,
directions. Perpendicular to the Galactic plane, the number density of AGB
stars is well described by an exponential function with a vertical scale height
of 300 pc. In the radial direction the number density of AGB stars is constant
up to R ~ 5 kpc, and then it decreases exponentially with a scale length of
\~1.6 kpc. This fall-off extends to at least 12 kpc, where the sample becomes
too small. The overall normalization implies that there are about 200,000 AGB
stars in the Galaxy. We estimate the [25]-[12] color distribution of AGB stars
for an unbiased volume-limited sample. By using a model-dependent
transformation between the color and mass-loss rate, Mdot, we constrain the
time dependence of Mdot. The results suggest that for 10^-6 Mo/yr < Mdot <
10^-5 Mo/yr the mass-loss rate increases exponentially with time. We find only
marginal evidence that the mass-loss rate increases with stellar mass.Comment: 15 pages, submitted to MNRA
A feasibility study for NOn-Traditional providers to support the management of Elderly People with Anxiety and Depression: the NOTEPAD study Protocol
BACKGROUND:
Anxiety and depression are common among older people, with up to 20% reporting such symptoms, and the prevalence increases with co-morbid chronic physical health problems. Access to treatment for anxiety and depression in this population is poor due to a combination of factors at the level of patient, practitioner and healthcare system. There is evidence to suggest that older people with anxiety and/or depression may benefit both from one-to-one interventions and group social or educational activities, which reduce loneliness, are participatory and offer some activity. Non-traditional providers (support workers) working within third-sector (voluntary) organisations are a valuable source of expertise within the community but are under-utilised by primary care practitioners. Such a resource could increase access to care, and be less stigmatising and more acceptable for older people.
METHODS:
The study is in three phases and this paper describes the protocol for phase III, which will evaluate the feasibility of recruiting general practices and patients into the study, and determine whether support workers can deliver the intervention to older people with sufficient fidelity and whether this approach is acceptable to patients, general practitioners and the third-sector providers. Phase III of the NOTEPAD study is a randomised controlled trial (RCT) that is individually randomised. It recruited participants from approximately six general practices in the UK. In total, 100 participants aged 65 years and over who score 10 or more on PHQ9 or GAD7 for anxiety or depression will be recruited and randomised to the intervention or usual general practice care. A mixed methods approach will be used and follow-up will be conducted 12 weeks post-randomisation.
DISCUSSION:
This study will inform the design and methods of a future full-scale RCT.
TRIAL REGISTRATION:
ISRCTN, ID: ISRCTN16318986 . Registered 10 November 2016. The ISRCTN registration is in line with the World Health Organization Trial Registration Data Set. The present paper represents the original version of the protocol. Any changes to the protocol will be communicated to ISRCTN
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